Delayed cure additive manufacturing

ABSTRACT

A method for manufacturing a part includes fabricating an object in an additive fabrication stage, the object including a solid mold forming a cavity in the shape of a part with uncured or incompletely cured build material disposed therein. The build material in the cavity is cured in a curing stage that occurs at least partially after the additive fabrication stage. The build material undergoes a phase change mechanism occurring during the additive fabrication stage and a distinct polymerization mechanism occurring during the curing stage and at least partly after the additive fabrication stage of the object and cures the build material by a polymerization process.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.17/031,212, filed on Sep. 24, 2020 entitled “Delayed Cure AdditiveManufacturing”.

BACKGROUND OF THE INVENTION

This invention relates to a manufacturing process with a delayed curingstep.

Some manufacturing techniques use molds to fabricate parts. A moldgenerally has a predefined shape and is filled with a build material(e.g., a molten material such as a molten metal or plastic). The buildmaterial solidifies, yielding the part. The part can then be removed,for example, by destroying or otherwise removing the mold.

Molds are often fabricated from metallic material (e.g., steel oraluminum) and are precision-machined to form the features of a desiredpart. When designing parts for molding, care must be taken to ensurethat the parts are compatible with the molding process. For example, thematerial used for the part, the desired shape and features of the part,the material of the mold, and the properties of the molding machine mustall be taken into account when designing a part.

SUMMARY OF THE INVENTION

In a broad aspect, a manufacturing process for fabricating a part usesadditive manufacturing techniques to fabricate an object including thepart in an uncured or incompletely cured form. In general, the additivefabrication is an iterative process, where the material that forms theobject is deposited incrementally, for example, in layers. During anadditive fabrication stage of the manufacturing process, the materialfor the part of the object, referred to as “build material,” isdeposited in a liquid phase.

In the additive fabrication stage, additive manufacturing techniques areused to fabricate the object to include a solid mold containing thebuild material of the part, for example with the solid mold forming acavity with a shape of the part. Rather than completely fabricating thesolid mold and then filling the mold with build material, uncured buildmaterial is incrementally added to the object as the mold is fabricated.

In the overall manufacturing process, which includes the additivefabrication stage as well as a subsequent or overlapping part curingstage, the build material for the part of the object undergoes twodistinct mechanisms: a phase change mechanism and a polymerizationmechanism.

The phase change mechanism occurs during the additive fabrication stageand causes a phase change of the build material from a liquid to anon-liquid (e.g., at least partially solid, semi-solid, and/orquasi-solid), where the phase change is generally not due topolymerization. In this non-liquid form the build material issufficiently solidified for subsequent incremental deposit of materialon to it (e.g., the non-liquid build material can support the weight ofincrementally added material and/or the force of the material as it isjetted to, for example, prevent mixing between the build material andthe support material).

The polymerization mechanism occurs after, or at least partly after, theadditive fabrication of the object during the curing stage. Thismechanism cures the build material by a polymerization process. In someexamples, the polymerization mechanism is initiated after additivefabrication of the object is complete. In other examples, thepolymerization mechanism is initiated before additive manufacturing iscomplete, for example, being initiated during the phase change mechanism(e.g., with both mechanisms being initiated at the same time, or thepolymerization mechanism being initiated during the phase changemechanism).

After the build material is sufficiently cured (e.g., sufficientlypolymerized) in the curing stage to allow removal of the mold, themanufacturing process enters a part removal stage for removal of themold. Removal of the mold yields the fabricated part.

In an general aspect, a method for manufacturing a part includesfabricating, in an additive fabrication stage, an object including buildmaterial for the part in an uncured or incompletely cured form and asolid mold forming a cavity with a shape of the part and containing thebuild material and curing the part, in a curing stage that occurs atleast partially after the additive fabrication stage. In the additivefabrication stage, material that forms the object is depositedincrementally including depositing build material for the part in aliquid phase and depositing material for the mold, and during theadditive fabrication stage the material for the mold solidifies to formthe solid mold. The build material undergoes a phase change mechanismand a distinct polymerization mechanism, the phase change mechanismoccurring during the additive fabrication stage and causing a phasechange of the build material from a liquid to a non-liquid. Thepolymerization mechanism occurs during the curing stage and occurs atleast partly after the additive fabrication stage of the object, andcures the build material by a polymerization process.

Aspects may include one or more of the following features.

The polymerization mechanism may be initiated after the additivefabrication stage. The polymerization mechanism may be initiated beforeadditive manufacturing stage is complete. The polymerization mechanismmay be initiated before completion of the phase change mechanism. Thephase change mechanism and the polymerization mechanism may be initiatedat the same time.

The method may further include, after the build material is at leastpartially cured in the curing stage, a part removal stage includingremoving the mold yield the fabricated part. The material for the moldmay solidify by a curing process. Curing the deposited mold material mayinclude causing the deposited mold material to polymerize. The moldmaterial may include a photo-curable material and the curing processincludes applying light to the deposited mold material. The material forthe mold may solidify by undergoing a physical phase change. Undergoingthe physical phase change may include allowing the material for the moldto cool.

The material for the mold may include a wax. Incrementally depositingmaterial for the object may include depositing a number of layers ofmaterial. At least some layers of material of the number of layers ofmaterial may be deposited using a jetting process. The material for themold deposited in a second layer of the number of layers may bedeposited on the build material deposited in a first layer of the numberof layers deposited prior to the second layer. At least some of thelayers may be added using two or more print heads.

Depositing the build material may include depositing a polymerizationinitiation catalyst. Depositing the layers may include depositing anumber of material components from a corresponding number of printheads, a first print head of the number of print heads depositing thepolymerization initiation catalyst. The polymerization initiationcatalyst may be mixed with the build material. Incrementally depositingthe layers may further include depositing at least some layers includingonly mold material.

The method may further include removing the solid mold. Removing thesolid mold may include at least one of dissolving the solid mold,mechanically removing the solid mold, and liquefying the solid mold. Thebuild material may include a wax after the phase change mechanism. Thebuild material may include a liquid prior to the phase change mechanism.Curing the part may include heating the build material. The buildmaterial may undergo a phase change of the build material to a liquidphase during the curing stage.

The build material may include a polymerization precursor. The curedmold material may be substantially stable under a build curingcondition. The cured build material may be substantially stable under amold removal condition. The non-liquid may be sufficiently solidifiedfor subsequent incremental deposit of material onto it during theadditive fabrication stage.

In another general aspect, a method receives a model representing a partto be fabricated. The method processes the model to determinecharacteristics (e.g., shape and material) of a mold that can be used tofabricate the part using the additive manufacturing techniques describedabove.

Aspects may have one or more of the following advantages.

Aspects advantageously are capable of fabricating parts with shapes andfrom materials that are not possible with conventional moldingtechniques (e.g., injection molding).

Aspects advantageously provide a more agile design process as comparedto conventional molding processes because the mold can be continuouslyrefined without incurring the costs and efforts associated with making anew mold for conventional molding.

Aspects are advantageously capable of producing polymers that haveimproved mechanical properties and are more isotropic as compared tothose produced by conventional inkjet printed parts.

Without wishing to be bound by theory, it is understood that the methodsand materials of the present disclosure may carry one or more potentialadvantages over the existing methods and materials in the field. Forexample, the methods and materials may allow for a delayed bulkpolymerization of the build materials, which could provide a curedmaterials containing polymers that are more isotropic and/or have a moreuniformed structure, as compared to cured materials prepared bylayer-by-layer polymerization. For another example, the methods may besuitable for using a wider range of polymerization conditions, includingwith slower rates of polymerization than typical.

Other features and advantages of the invention are apparent from thefollowing description, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an additive manufacturing printer.

FIG. 2 shows a first state of a manufacturing process.

FIG. 3 shows a second state of the manufacturing process.

FIG. 4 shows a third state of the manufacturing process yielding afabricated object.

FIG. 5 shows a curing process yielding the fabricated object with acured part therein.

FIG. 6 shows a mold material removal process yielding a fabricated part.

FIG. 7 shows a second manufacturing process.

FIG. 8 shows a first state of a third manufacturing process.

FIG. 9 shows a second state of the third manufacturing process.

FIG. 10 shows a third state of the third manufacturing process yieldinga fabricated object.

FIG. 11 shows a curing process yielding the fabricated object with acured part therein.

FIG. 12 shows a mold material removal process yielding a fabricatedpart.

FIG. 13 shows a first state of a fourth manufacturing process.

FIG. 14 shows a second state of the fourth manufacturing process.

FIG. 15 shows a third state of the fourth manufacturing process,yielding a fabricated object.

FIG. 16 shows a curing process yielding the fabricated object with acured part therein.

FIG. 17 shows a mold removal process yielding a fabricated part.

DETAILED DESCRIPTION 1 Overview

The description below relates to a manufacturing process that usesadditive fabrication, for example, using a jetting-based 3D printer 100as shown in FIG. 1 . Very generally, the manufacturing process includesthree temporal phases: an additive fabrication stage, a part curingstage, and a part removal stage. As is described in greater detailbelow, in some examples, the part curing stage occurs entirely after theadditive fabrication stage. In other examples the additive fabricationstage and the part curing stage partially overlap.

In the additive fabrication stage, additive fabrication is used tofabricate an object 104 including a solid (e.g., cured) mold structure111 that forms a cavity (e.g., closed structure or open vessel) defininga shape of the part 112, where the cavity is filled with a semi-solid,uncured or partially cured material in the shape of the part 112. Thesolid mold structure 111 and/or the semi-solid material are added, layerby layer, to form the object 104.

In the part curing stage, at least some of which occurs at a time aftercompletion of the additive fabrication stage, the object 104 includingthe filled mold structure 111 undergoes a curing process forpolymerizing the material in the cavity.

In the additive manufacturing stage and the part curing stage, thematerial used to form the part 112 (sometimes referred to as “buildmaterial) undergoes two distinct mechanisms: a phase change mechanismand a polymerization mechanism.

The phase change mechanism occurs during the additive fabrication stageand causes a phase change of the build material from a liquid to anon-liquid (e.g., at least partially solid, semi-solid, and/orquasi-solid, where these three terms may be used interchangeablyherein). In this non-liquid form the build material is sufficientlysolidified for subsequent incremental deposit of material on to it(e.g., the non-liquid build material can support the weight or force ofincrementally added material).

The polymerization mechanism occurs after, or at least partly after, theadditive fabrication of the object 104 during the curing stage. Thismechanism cures the build material by a polymerization process. In someexamples, the polymerization mechanism is initiated after additivefabrication of the object is complete. In other examples, thepolymerization mechanism is initiated before additive manufacturing iscomplete, for example, being initiated during the phase change mechanism(e.g., with both mechanisms being initiated at the same time, or thepolymerization mechanism being initiated after initiation and during thephase change mechanism).

In the part removal stage, the solid mold structure 111 is removed,yielding the part 112. In some examples, the part removal stage occursafter the part curing stage. But in other examples, the part removalstage may overlap with the part curing stage (e.g., the part 112 isstill curing but is sufficiently cured for removal from the solid moldstructure 111).

2 Printer

In the additive fabrication stage, the printer 100 uses jets 102(inkjets) to emit material for deposition of layers to form the object104 (shown partially fabricated in FIG. 1 ). For the printer illustratedin FIG. 1 , the object 104 is fabricated on a build platform 106, whichis controlled to move relative to the jets (i.e., along an x-y plane) ina raster-like pattern to form successive layers, and in this examplealso to move relative to the jets (i.e., along a z-axis) to maintain adesired separation of the jets and the surface of thepartially-fabricated object 104.

As illustrated, there are multiple jets 108, 110, for example with afirst jet 108 being used to emit a mold material 113 to form a solid(e.g., cured or semi-cured) mold structure 111 of the object 104, and asecond jet 110 being used to emit build material 114 to form an uncuredor partially cured, semi-solid (e.g., a gel or a wax) part 112 in theobject 104. Additional details of the properties of the mold material113 and the build material 114 are described below.

A sensor 116 (sometimes referred to as a scanner) is positioned relativeto (e.g., above) the object under fabrication 104 and is used todetermine physical characteristics of the partially fabricated object.For example, the sensor 116 measures one or more of the surface geometry(e.g., a depth map characterizing the thickness/depth of the partiallyfabricated object) and subsurface characteristics (e.g., in the nearsurface comprising, for example, 10s or 100s of deposited layers). Thecharacteristics that may be sensed can include one or more of a materialdensity, material identification, and a curing state. Very generally,the measurements from the sensor 116 are associated with athree-dimensional (i.e., x, y, z) coordinate system where the x and yaxes are treated as spatial axes in the plane of the build surface andthe z axis is a height axis (i.e., growing as the object is fabricated).

In some examples, in the context of a digital feedback loop for additivefabrication, the additive manufacturing system builds the object byprinting layers. The sensor 116 captures the 3D scan information afterthe printer 100 prints one or more layers. For example, the sensor 116scans the partial object (or empty build platform), then the printerprints a layer (or layers) of material(s). Then, the sensor 116 scansthe (partially built) object again. The new depth sensed by the sensor116 should be at a distance that is approximately the old depth minusthe thickness of layer (this assumes that the sensor 116 is positionedon the top of the of the object being built and the object is beingbuilt from the bottom layer to the top layer and the distance betweenthe sensor 116 and the build platform is unchanged). Various types ofsensing such as optical coherence tomography (OCT) or laser profilometrycan be used to determine depth and volumetric information related to theobject being fabricated.

A controller 118 uses a model 120 of the object to be fabricated tocontrol motion of the build platform 106 using a motion actuator 122(e.g., providing three degrees of motion) and control the emission ofmaterial from the jets 102 according to non-contact feedback of theobject characteristics determined via the sensor 116.

3 Manufacturing Process 3.1 Example 1

Referring to FIG. 2 , the printer 100 (only the jets 102 of the printer100 are shown for simplicity in FIG. 2 ) is in the midst of the additivefabrication stage of the manufacturing process where an object 104including a three-dimensional, substantially “egg-shaped” semi-solidpart 112 (shown in a two-dimensional cross-section for simplicity inFIG. 2 ) is formed inside a solid mold structure 111. In this example,the semi-solid part 112 remains in an uncured state throughout theadditive fabrication stage and the part curing stage begins byinitiating the polymerization mechanism after the additive fabricationstage is complete.

As is described above, the semi-solid part 112 is formed from asemi-solid build material 114 (e.g., a wax or gel) deposited by thesecond jet 110. In this example, the build material 114 that isdeposited by the second jet 110 is a curable precursor materialincluding a mixture of a monomer and a polymerization initiationcatalyst. The build material 114 is emitted from the second jet 110 as aliquid. During deposition, the build material 114 is sometimes describedas being in a build depositing condition. The deposited build material114 undergoes the phase change mechanism wherein the build materialundergoes a physical phase change to become a semi-solid after beingdeposited (e.g., by cooling). In this example, the polymerizationmechanism is not yet initiated at this stage, and the semi-solid buildmaterial 114 is described as being in a pre-curing condition.

The solid mold structure 111 is formed from a mold material 113 (e.g., aUV curable polymer) deposited by the first jet 108. In this example, themold material 113 is emitted from the first jet 108 as a liquid. Duringdeposition, the mold material 113 is sometimes described as being in amold depositing condition. At some time after the mold material isdeposited, curing of the mold material commences. During curing, themold material 113 is described as being in a mold curing condition. Themold material 113 in the mold curing condition undergoes a chemicalphase change to become solid after being deposited (e.g., by undergoinga UV curing process). The solid mold material 113 is sometimes describedas being in a mold pre-removal condition.

In FIG. 2 , a number of layers of the object (some including bothsemi-solid, uncured build material and solidified mold material) areshown having been deposited such that roughly a third of the egg shapedsemi-solid part 112 is formed in the solid mold structure 111.

Referring to FIG. 3 , as the additive fabrication stage progresses, theegg shaped semi-solid part 112 begins to take on the appearance of anegg, where some parts of the “egg shell” overhang parts of the interiorof the egg. That is, in certain areas 124 of the print surface 126, thesolid mold structure 111 is specified to lay on top of the semi-solidpart 112 (i.e., the solid mold structure 111 overhangs the semi-solidpart 112). In the overhanging areas 124, the mold material 113 isdeposited onto the semi-solid, deposited build material 114 of thesemi-solid part 112, which serves as a support surface for depositingthe mold material 113. The semi-solid, deposited build material 114 ofthe semi-solid part 112 holds the deposited mold material 113 in placebefore and during its solidification (e.g. curing).

Referring to FIG. 4 , eventually the additive fabrication stage of themanufacturing process completes, yielding the fabricated object 104including the semi-solid, uncured part 112 contained in the solid moldstructure 111.

The semi-solid, uncured part 112 shown in FIG. 4 includes a complexstructure 126. In some examples, the complex structure 126 is a featurethat will still be included in the part 112 after curing. The complexstructure 126 may be a structure that would be difficult to form usingconventional molding techniques. In other examples, the complexstructure 126 is included to compensate for effects of the curingprocess on the semi-solid part 112. For example, the complex structure126 may include additional build material 114 that gravity feeds intothe cavity formed in the mold structure 111 when the build material 114of the semi-solid part 112 shrinks during curing. Alternatively, thecomplex structure 126 may be an open space that allows for expansion ofthe build material 114 of the semi-solid part 112 during curing. In yetanother example, the complex structure 126 establishes a vent (notshown) to the environment in the mold structure 111 to allow gasesproduced during the curing process to escape. It should be appreciatedthat any number of other complex structures 126 can be formed forvarious other reasons.

Referring to FIG. 5 , in the part curing stage of the manufacturingprocess, the fabricated object 104 is subjected to a curing process,wherein the polymerization mechanism is initiated to cure the semi-solidpart 112. The part curing stage yields a cured object 504 with a curedpart 512 contained in the solid mold structure 111. During the partcuring stage, the semi-solid build material 114 of the part 112 issometimes described as being in the build curing condition.

The curing process in FIG. 5 is a heating-based process. Very generally,the heating process activates the polymerization initiation catalyst(i.e., initiates the polymerization mechanism) included in the buildmaterial 114, which in turn reacts with the monomer included in thebuild material 114 to cause polymerization of the build material 114 ofthe semi-solid part 112, yielding the cured object 504 with the cured(or sufficiently cured) part 512. It should be appreciated that othertypes of curing processes (e.g., UV curing or curing by a curing agent)can be used. In some examples, the curing process applies differenttemperatures at different times to control the curing process.

Referring to FIG. 6 , in the part removal stage of the manufacturingprocess, the solid mold structure 111 is removed from the cured object504, yielding the cured (or sufficiently cured) part 512. During thepart removal stage, the solid mold material 113 of the solid moldstructure 111 is sometimes described as being in a mold removalcondition.

In the example of FIG. 6 , the solid mold structure 111 is soluble(e.g., water or other solvent soluble), and is removed by bathing thecured object 504 in water 130 or some other solvent to dissolve thesolid mold structure. In other examples, the solid mold structure isphysically removed (e.g., by breaking the solid mold structure 111 off),removed with heat, chemically removed (e.g., by a chemical reaction), orsome combination of the aforementioned removal techniques.

3.2 Example 2

Referring to FIG. 7 , in the example described above two jets are usedin the additive fabrication stage of the manufacturing process, one jetfor depositing the mold material and another jet for depositing buildmaterial that is a mixture of a monomer and a polymerization initiationcatalyst. But in the example of FIG. 7 , the monomer and thepolymerization initiation catalyst are deposited from separate jets andmix at a later time (e.g., when deposited or during the curing process).

That is, in FIG. 7 , three jets 708, 709, 710 are used in the additivefabrication stage of the manufacturing process, with a first jet 708being used to emit a mold material 713 to form a solid (e.g., cured orsemi-cured) mold structure 711 of the object 704, a second jet 709 beingused to emit a monomer 714 as a first component of the semi-solid (e.g.,a gel or a wax), uncured part 712 in the object 704, and a third jet 710being used to emit a polymerization initiation catalyst 715 (jetted, forexample, in a diluent-solvent) to as a second component of thesemi-solid, uncured part 712 in the object 704. In some examples, boththe monomer 714 and the polymerization initiation catalyst 715 areemitted as a liquid and undergo a phase change mechanism (e.g., cooling)to become semi-solid. Besides this difference in how the build materialof the semi-solid part 712 is formed, the manufacturing process forforming the cured part is much the same as the process described abovefor FIGS. 1-6 .

3.3 Example 3

Referring to FIG. 8 , in another example of the manufacturing process,the printer 100 (including three jets 802 in this example) is in themidst of the additive fabrication stage of the manufacturing processwhere an object 804 including a three-dimensional, substantially“egg-shaped” semi-solid part 812 (shown in a two-dimensional aspect forsimplicity in FIG. 8 ) is formed inside a solid mold structure 811,which is in turn formed inside of (e.g., supported by) a wax supportstructure 817. In this example, the semi-solid part 812 remains in anuncured state throughout the additive fabrication stage and the partcuring stage begins by initiating the polymerization mechanism after theadditive fabrication stage is complete.

As was the case in previous examples, the semi-solid part 812 is formedfrom a semi-solid build material 814 (e.g., a wax or gel) deposited inliquid form prior to the phase change mechanism by a second jet 810. Inthis example, the build material 814 that is deposited by the second jet810 is a curable precursor material including a monomer and apolymerization initiation catalyst. The build material 814 is emittedfrom the second jet 810 as a liquid. During deposition, the buildmaterial 814 is sometimes described as being in a build depositingcondition. The deposited build material 814 undergoes the phase changemechanism wherein the build material undergoes a physical phase changeto become a semi-solid after being deposited (e.g., by cooling). In thisexample, the polymerization mechanism is not yet initiated at the stage,and the semi-solid build material 814 is sometimes described as being ina build pre-curing condition.

The solid mold structure 811 is formed from a mold material 813 (e.g., aUV curable polymer) deposited by a first jet 808. In this example, themold material 813 is emitted from the first jet 808 as a liquid. Duringdeposition, the mold material 813 is sometimes described as being in amold depositing condition. At some time after the mold material 813 isdeposited, curing of the mold material 813 commences. During the curingprocess, the mold material 813 is described as being in a mold curingcondition. The mold material 813 in the mold curing condition undergoesa chemical phase change to become solid (sometimes described as being ina mold pre-removal condition) after being deposited (e.g., by undergoinga UV curing process).

The wax support structure 817 is formed from a wax support material 819(e.g., ester waxes, amide waxes, urethane waxes, or urea waxes)deposited by a third jet 809. In this example, the wax support material819 is emitted from the third jet 809 as a liquid and undergoes aphysical phase change to become a solid or semi-solid after beingdeposited (e.g. by cooling).

In FIG. 8 , a number of layers of the object (some including semi-solid,uncured build material, solidified mold material, and wax supportmaterial) are deposited such that roughly a third of the egg shapedsemi-solid part 812 is formed in the solid mold structure 811 and waxsupport structure 817.

Referring to FIG. 9 , as the additive fabrication stage progresses, theegg shaped semi-solid part 812 begins to take on the appearance of anegg, where some parts of the “egg shell” overhang parts of the interiorof the egg. That is, in certain areas 824 of the print surface 826, thewax support structure 817 is specified to lay on top of the solid moldstructure 811 (i.e., the wax support structure 817 overhangs the solidmold structure 811), and the solid mold structure 811 is specified tolay on top of the semi-solid part 812 (i.e., the solid mold structure811 overhangs the semi-solid part 812). In the overhanging areas 824,the mold material 813 is deposited onto the semi-solid, deposited buildmaterial 814 of the semi-solid part 812, which serves as a supportingsurface for depositing the mold material 813. Similarly, the wax supportmaterial 819 is deposited onto the solid mold material 813 of the solidmold structure 811 in the overhanging areas 824. That is, thesemi-solid, deposited build material 814 of the semi-solid part 812holds the deposited mold material 813 in place before and during itssolidification (e.g., curing) and the mold material 813 of the solidmold structure 811 holds the wax support material 819 in place as itcools.

Referring to FIG. 10 , eventually the additive fabrication stage of themanufacturing process completes, yielding the fabricated object 804including the semi-solid part 812 contained in the solid mold structure811, which is in turn contained in the wax support structure 817. Thesemi-solid, uncured part 812 of the fabricated object 804 at this stageis sometimes described as being in a build pre-curing condition.

Referring to FIG. 11 , the fabricated object 804 is then subjected to acombined part removal/curing stage of the manufacturing process toremove the wax support structure 817 and cure the semi-solid part 812.In the curing aspect of the part removal/curing stage, thepolymerization mechanism is initiated to cure the semi-solid part 112.The part removal/curing stage yields a cured part 912 contained in thesolid mold structure 811. In some examples, the part removal/curingstage substantially simultaneously removes the wax support structure 817and cures the semi-solid part 812. In other examples, the removal andcuring occur in two sequential steps. While the semi-solid part 112undergoes the curing process in the part curing stage, it is sometimesdescribed as being in a build curing condition.

The curing process shown in FIG. 11 is a heating-based process. Verygenerally, the heating process melts away the wax support structure 817and activates the polymerization initiation catalyst (i.e., initiatesthe polymerization mechanism) included in the build material 814, whichin turn reacts with the monomer included in the build material 814 tocause polymerization of the build material 814 of the semi-solid part812. This yields the cured (or sufficiently cured) part 912 contained inthe solid mold structure 811.

In some examples, the heating process operates at a single temperaturethat is sufficient to both melt the wax support structure and cure thebuild material 814. In other examples, the curing process appliesdifferent temperatures at different times to control the melting and/orcuring process. It should be appreciated that other types of curingprocesses (e.g., UV curing or curing by a curing agent) can also beused.

Referring to FIG. 12 , in the part removal stage of the manufacturingprocess, the solid mold structure 811 is removed from the cured (orsufficiently cured) part 512. During the removal stage, the solid moldmaterial 813 of the solid mold structure 811 is sometimes described asbeing in a mold removal condition.

In the example of FIG. 12 , the solid mold structure 811 is soluble(e.g., water or other solvent soluble), and is removed by bathing thecured part 912 contained in the solid mold structure 811 in water 830 orsome other solvent to dissolve the solid mold structure 811. In otherexamples, the solid mold structure 811 is physically removed (e.g., bybreaking the solid mold structure 811 off), removed with heat,chemically removed (e.g., by a chemical reaction), or some combinationof the aforementioned removal techniques.

3.4 Example 4

Referring to FIG. 13 , in another example of the manufacturing process,the printer 100 (only the jets 1302 of the printer 100 are shown forsimplicity in FIG. 13 ) is in the midst of the additive fabricationstage of the manufacturing process where an object 1304 including athree-dimensional, substantially “egg-shaped” semi-solid part 1312(shown in a two-dimensional cross-section for simplicity in FIG. 13 ) isformed inside a solid mold structure 1311. In this example, thesemi-solid part 1312 begins the curing stage, including undergoing thepolymerization mechanism, during the additive fabrication stage. Thecuring stage continues after the additive fabrication stage is complete.

As is described above, the semi-solid part 1312 is formed from asemi-solid build material 1314 (e.g., a wax or gel) deposited by thesecond jet 1310. In this example, the build material 1314 that isdeposited by the second jet 1310 is a curable precursor materialincluding a mixture of a monomer and a polymerization initiationcatalyst. The build material 1314 is emitted from the second jet 1310 asa liquid. During deposition, the build material 1314 is sometimesdescribed as being in a build depositing condition. The deposited buildmaterial 1314 undergoes the phase change mechanism wherein the buildmaterial undergoes a physical phase change to become a semi-solid afterbeing deposited (e.g., by cooling). In this example, the polymerizationmechanism is initiated either simultaneously with the phase changemechanism or at sometime soon thereafter (e.g., by application of UVlight or some other trigger) such that the part curing stage commences.In the event that the polymerization mechanism is initiated after thephase change mechanism, the semi-solid build material 1314 is describedas being in a pre-curing condition when the phase change mechanism iscomplete and the polymerization mechanism is not yet initiated. Once thepolymerization mechanism, the build material 1314 is described as beingin a build curing condition.

The solid mold structure 1311 is formed from a mold material 1313 (e.g.,a UV curable polymer) deposited by the first jet 1308. In this example,the mold material 1313 is emitted from the first jet 1308 as a liquid.During deposition, the mold material 1313 is sometimes described asbeing in a mold depositing condition. At some time after the moldmaterial is deposited, curing of the mold material commences. Duringcuring, the mold material 1313 is described as being in a mold curingcondition. The mold material 1313 in the mold curing condition undergoesa chemical phase change to become solid after being deposited (e.g., byundergoing a UV curing process). The solid mold material 1313 issometimes described as being in a mold pre-removal condition.

In FIG. 13 a number of layers of the object (some including bothsemi-solid, uncured build material and solidified mold material) areshown having been deposited such that roughly a third of the egg shapedsemi-solid part 1312 is formed in the solid mold structure 1311.

Referring to FIG. 14 , as the additive fabrication stage progresses, theegg shaped semi-solid part 1312 begins to take on the appearance of anegg, where some parts of the “eggshell” overhang parts of the interiorof the egg. That is, in certain areas 1324 of the print surface 1326,the solid mold structure 1311 is specified to lay on top of thesemi-solid part 1312 (i.e., the solid mold structure 1311 overhangs thesemi-solid part 1312). In the overhanging areas 1324, the mold material1313 is deposited onto the semi-solid, deposited build material 1314 ofthe semi-solid part 1312, which serves as a support surface fordepositing the mold material 1313. The semi-solid, deposited buildmaterial 1314 of the semi-solid part 1312 holds the deposited moldmaterial 1313 in place before and during its solidification (e.g.curing).

Referring to FIG. 15 , eventually the additive fabrication stage of themanufacturing process completes, yielding the fabricated object 1304including the semi-solid, partially cured part 1312 contained in thesolid mold structure 1311.

Referring to FIG. 16 , the part curing stage of the manufacturingprocess continues and eventually yields a cured object 1604 with a curedpart 1612 contained in the solid mold structure 1311.

Note that there is no additional curing process in FIG. 16 —thepolymerization mechanism initiated during the additive fabrication stagesimply continues without any additional influence. However, it should benoted that there could be additional steps taken to cure the partiallycured part 1312 after the additive fabrication stage is complete. Forexample, the fabricated object 1304 including the partially cured part1312 could be subjected to a heating step (as described above) after theadditive fabrication stage is complete.

Referring to FIG. 17 , in the part removal stage of the manufacturingprocess, the solid mold structure 1311 is removed from the cured object1604, yielding the cured (or sufficiently cured) part 1612. During thepart removal stage, the solid mold material 1313 of the solid moldstructure 1311 is sometimes described as being in a mold removalcondition.

In the example of FIG. 6 , the solid mold structure 1311 is soluble(e.g., water or other solvent soluble), and is removed by bathing thecured object 1604 in water 1730 or some other solvent to dissolve thesolid mold structure. In other examples, the solid mold structure isphysically removed (e.g., by breaking the solid mold structure 1311off), removed with heat, chemically removed (e.g., by a chemicalreaction), or some combination of the aforementioned removal techniques.

4 Material Properties

Very generally, the build and mold materials described above are chosensuch that an uncured or partially cured part can be fabricated, where atleast some of the curing of the fabricated part occurs in the solid moldat some time after fabrication of the part.

4.1 Build Materials

In some examples, the build material is a mixture of a precursor and apolymerization initiation catalyst and possibly a “gelling” component(e.g., a wax). The build material is deposited in the build depositingcondition (e.g., as a liquid) and, by a phase change mechanism, “gels”to form a semi-solid material (sometimes described as a pre-curedcondition). The gelling of the build material is caused by a physicalstate change (e.g., cooling) and is not caused by chemical changes suchas polymerization or partial polymerization (though in some examples, itis caused by a non-polymerization chemical change). In some examples, ata time during the additive fabrication stage or after the additivemanufacturing stage is complete, a part curing stage initiates apolymerization mechanism, causing the precursor and the polymerizationinitiation catalyst of the build material to react, curing the buildmaterial in the build curing condition (e.g., by polymerization). Insome examples, the curing process of the part curing stage causesliquification of the build material.

In some embodiments, the build material is deposited (e.g., jetted)under a build depositing condition (e.g., build jetting condition).

In some embodiments, the build material is cured under a build curingcondition.

In some embodiments, the build material is a liquid under the builddepositing condition (e.g., the build jetting condition).

In some embodiments, the build material is a wax when in the pre-curingcondition.

In some embodiments, the build material has a melting point being thesame or lower than the temperature of the build depositing condition.

In some embodiments, the build material has viscosity ranging from about5 cp to about 100 cp at the temperature of the build depositingcondition.

In some embodiments, upon deposition, the build material is converted toa solid, semi-solid, or quasi-solid(e.g., via a phase change).

In some embodiments, upon deposition, the build material is converted toa solid, semi-solid, or quasi-solid by cooling.

In some embodiments, the build material is converted to a solid by anon-polymerization chemical change.

In some embodiments, the build material is UV curable.

In some embodiments, the build material is thermally curable.

In some embodiments, the build material is chemically curable by acuring catalyst or a curing agent.

In some embodiments, the build material is substantially stable (e.g.,chemically and/or physically) toward the mold material.

In some embodiments, the build material is substantially stable (e.g.,chemically and/or physically) under the mold curing condition (e.g.,when exposed to UV radiation).

In some embodiments, the build material is substantially stable (e.g.,chemically and/or physically) toward the cured mold material.

In some embodiments, the build material comprises a precursor (e.g., amonomer or a protected monomer) for a polymer.

In some embodiments, the precursor is a precursor for a polyamide (e.g.,polyamide 6).

In some embodiments, the precursor is a precursor for a polyethersulfone(PES).

In some embodiments, the precursor comprises an epoxide, a polyepoxide,or a combination thereof.

In some embodiments, the precursor comprises a benzoxazine.

In some embodiments, the precursor is a precursor for ring openingpolymerization

In some embodiments, the precursor comprises a cyclic olefin (e.g., ringopening metathesis polymerization).

In some embodiments, the precursor comprises an acrylate.

In some embodiments, the precursor is a precursor for thiol-enepolymerization.

In some embodiments, the precursor comprises a thiol agent, an alkenylagent, or a combination thereof.

In some embodiments, the precursor is a precursor for bulkpolymerization.

In some embodiments, the build material comprises a curing catalyst.

In some embodiments, the curing catalyst cures the build material butdoes not cure the mold material.

In some embodiments, the build material comprises a curing agent (e.g.an agent that co-polymerizes with the polymer precursor, modifies thepolymer, or cross-links the polymer).

In some embodiments, the curing agent cures the build material but doesnot cure the mold material.

In some embodiments, the curing agent comprises an amide, an anhydride,or a combination thereof.

4.1.1 Build Curing Conditions

In some embodiments, the build curing condition comprises or isinitiated by irradiation (e.g., visible light or UV).

In some embodiments, the build curing condition comprises or isinitiated by an elevated temperature condition.

In some embodiments, the build curing condition results from adding acuring catalyst.

In some embodiments, the build curing condition results from adding acuring agent (e.g. an agent that co-polymerizes with the polymerprecursor, modifies the polymer, or cross-links the polymer).

In some embodiments, the build curing condition is substantially free ofair (e.g., oxygen).

In some embodiments, the build curing condition is substantially free ofwater.

4.1.2 Cured Build Materials

In some embodiments, the cured build material is substantially stable(e.g., chemically and/or physically) toward the cured mold material

In some embodiments, the cured build material is substantially stable(e.g., chemically and/or physically) under the mold removal condition.

In some embodiments, the build material comprises a polymer.

In some embodiments, the polymer is a polyamide (e.g., polyamide 6).

In some embodiments, the polymer is a polyethersulfone (PES).

In some embodiments, the polymer is formed by polymerization of epoxide.

In some embodiments, the polymer is formed by co-polymerization betweenepoxide, and an amide or anhydride.

In some embodiments, the polymer is a benzoxazine polymer.

In some embodiments, the polymer is formed by ring openingpolymerization (e.g., ring opening metathesis polymerization).

In some embodiments, the polymer is an acrylate polymer.

In some embodiments, the polymer is a thiol-ene polymer.

4.2 Mold Materials

In some examples, the mold material is curable during the additivefabrication stage such that the solid mold structure can be at leastpartially cured (e.g., via a chemical change such as polymerization) asit is built. In some examples, the mold material is deposited in a molddepositing condition (e.g., as a liquid). The deposited mold material issometimes described as being in a mold pre-curing condition. Thedeposited mold material enters a mold curing condition whensolidification of the mold material is triggered by an excitationsignal. In some examples, the excitation signal includes ultravioletillumination emitted by a curing signal generator (e.g., a UV lamp),which triggers curing of the mold material shortly after it is emitted.In other examples, an excitation signal (e.g., optical, RF, etc.) is notnecessarily used. Rather, the curing is triggered chemically, forexample, by mixing multiple components before jetting, or jettingseparate components that mix and trigger curing. In some examples, thecured mold material is described as being in a mold pre-removalcondition.

In general, when the mold material of the solid mold structure is in themold pre-removal condition, it is able to resist the process used tocure the part (e.g., heating) without deformation or break-down. Themold material is removable from cured part after curing is complete bysubjecting the mold material to a mold removal condition.

In some embodiments, the mold material is deposited (e.g., jetted) undera mold depositing condition (e.g., mold jetting condition).

In some embodiments, the mold material is cured under a mold curingcondition.

In some embodiments, the mold material or the cured mold material isremoved under a mold removal condition.

In some embodiments, the mold material is a liquid under the molddepositing condition (e.g., the mold jetting condition).

In some embodiments, the mold material is a wax.

In some embodiments, the mold material has a melting point being thesame or lower than the temperature of the mold depositing condition

In some embodiments, the mold material has viscosity ranging from about5 cp to about 100 cp at the temperature of the mold depositingcondition.

In some embodiments, upon deposition, the mold material is converted toa solid (e.g., via a phase change).

In some embodiments, upon deposition, the mold material is converted toa solid by cooling.

In some embodiments, upon deposition, the mold material is converted toa solid by curing.

In some embodiments, the mold material is UV curable.

In some embodiments, the mold material is thermally curable.

In some embodiments, the mold material is curable toward a curingcatalyst or a cuing agent.

In some embodiments, the mold material is substantially stable (e.g.,chemically and/or physically) toward the build material.

In some embodiments, the mold material comprises a polymer precursor(e.g., a monomer).

In some embodiments, the mold material comprises a non-reacting compound(e.g., a wax).

In some embodiments, the mold material comprises a curing catalyst.

In some embodiments, the curing catalyst cures the mold material butdoes not cure the build material.

In some embodiments, the mold material comprises a curing agent (e.g. anagent that co-polymerizes with the polymer precursor, modifies thepolymer, or cross-links the polymer).

In some embodiments, the curing agent cures the mold material but doesnot cure the build material.

4.2.1 Mold Curing Conditions

In some embodiments, the mold curing condition comprises or is initiatedby irradiation (e.g., visible light or UV).

In some embodiments, the mold curing condition comprises or is initiatedby an elevated temperature condition.

In some embodiments, the mold curing condition results from adding acuring catalyst.

In some embodiments, the mold curing condition results from adding acuring agent (e.g. an agent that co-polymerizes with the polymerprecursor, modifies the polymer, or cross-links the polymer).

In some embodiments, the mold curing condition is substantially free ofair (e.g., oxygen).

In some embodiments, the mold curing condition is substantially free ofwater.

4.2.2 Cured Mold Materials

In some embodiments, the cured mold material is substantially stable(e.g., chemically and/or physically) toward the build material

In some embodiments, the cured mold material is substantially stable(e.g., chemically and/or physically) under the build curing condition.

In some embodiments, the cured mold material comprises a polymer.

4.2.3 Mold Removal Conditions

In some embodiments, the mold removal condition comprises adding asolvent, thereby dissolving the cured mold material.

In some embodiments, the mold removal condition comprises mechanicallyremoving the cured mold material.

In some embodiments, the mold removal condition comprises converting themold material from a solid to a liquid (e.g., via a phase change).

5 Alternatives

While the above examples are described in the context of a feedbackbased additive fabrication process, it is noted that the describedprocess is equally applicable to non-feedback based or conventionaladditive fabrication processes.

The egg-like structures described above are simple examples of partsthat can be fabricated using the described processes. But it should benoted the described processes are not limited to fabricating thesesimple shapes. Indeed, many other types of parts with more (or less)complex shapes can be (and likely would be) fabricated using thedescribed processes.

In the examples described above, the build material is assumed to behomogenous. But it is possible that non-homogenous build materials couldbe used to fabricate the semi-solid part. For example, an “egg yolk” ofa different build material could be included in the semi-solid part.

In the examples described above, the build material assumes a semi-solidstate after it is deposited. But it is possible that the build materialcould be in a liquid state after being deposited. In such cases, surfacetension of the liquid build material would be able to support any moldmaterial deposited on the liquid build material before it ispolymerized.

In some examples, the solid mold structure and the semi-solid, uncuredor partially cured part are formed at the same time, layer-by-layer. Insome examples, multiple layers of the solid mold structure are depositedand then the cavity formed by the multiple layers of the solid moldstructure is filled with build material.

6 Implementations

The approaches described above can be implemented, for example, using aprogrammable computing system executing suitable software instructionsor it can be implemented in suitable hardware such as afield-programmable gate array (FPGA) or in some hybrid form. Forexample, in a programmed approach the software may include procedures inone or more computer programs that execute on one or more programmed orprogrammable computing system (which may be of various architecturessuch as distributed, client/server, or grid) each including at least oneprocessor, at least one data storage system (including volatile and/ornon-volatile memory and/or storage elements), at least one userinterface (for receiving input using at least one input device or port,and for providing output using at least one output device or port). Thesoftware may include one or more modules of a larger program. Themodules of the program can be implemented as data structures or otherorganized data conforming to a data model stored in a data repository.

The software may be stored in non-transitory form, such as beingembodied in a volatile or non-volatile storage medium, or any othernon-transitory medium, using a physical property of the medium (e.g.,surface pits and lands, magnetic domains, or electrical charge) for aperiod of time (e.g., the time between refresh periods of a dynamicmemory device such as a dynamic RAM). In preparation for loading theinstructions, the software may be provided on a tangible, non-transitorymedium, such as a CD-ROM or other computer-readable medium (e.g.,readable by a general or special purpose computing system or device), ormay be delivered (e.g., encoded in a propagated signal) over acommunication medium of a network to a tangible, non-transitory mediumof a computing system where it is executed. Some or all of theprocessing may be performed on a special purpose computer, or usingspecial-purpose hardware, such as coprocessors or field-programmablegate arrays (FPGAs) or dedicated, application-specific integratedcircuits (ASICs). The processing may be implemented in a distributedmanner in which different parts of the computation specified by thesoftware are performed by different computing elements. Each suchcomputer program is preferably stored on or downloaded to acomputer-readable storage medium (e.g., solid state memory or media, ormagnetic or optical media) of a storage device accessible by a generalor special purpose programmable computer, for configuring and operatingthe computer when the storage device medium is read by the computer toperform the processing described herein. The system may also beconsidered to be implemented as a tangible, non-transitory medium,configured with a computer program, where the medium so configuredcauses a computer to operate in a specific and predefined manner toperform one or more of the processing steps described herein.

A number of embodiments of the invention have been described.Nevertheless, it is to be understood that the foregoing description isintended to illustrate and not to limit the scope of the invention,which is defined by the scope of the following claims. Accordingly,other embodiments are also within the scope of the following claims. Forexample, various modifications may be made without departing from thescope of the invention. Additionally, some of the steps described abovemay be order independent, and thus can be performed in an orderdifferent from that described.

A number of embodiments of the invention have been described.Nevertheless, it is to be understood that the foregoing description isintended to illustrate and not to limit the scope of the invention,which is defined by the scope of the following claims. Accordingly,other embodiments are also within the scope of the following claims. Forexample, various modifications may be made without departing from thescope of the invention. Additionally, some of the steps described abovemay be order independent, and thus can be performed in an orderdifferent from that described.

1. A method comprising: fabricating a three-dimensional structure including a plurality of materials, the fabricating including: emitting a first phase change material of the plurality of phase change materials at a first printing temperature above a first phase change temperature of the first phase change material, wherein the first phase change material cools to a first stable temperature below the first phase change temperature after the emitting, and emitting a second phase change material of the plurality of phase change materials at a second printing temperature above a second phase change temperature of the second phase change material, the second phase change material being curable by a chemical reaction at a curing temperature greater than the second printing temperature, wherein the second phase change material cools to a second stable temperature below the second phase change temperature after the emitting; wherein, upon completion of fabrication of the three-dimensional structure, the first phase change material encases the second phase change material in an uncured state.
 2. The method of claim 1 further comprising initiating curing of the second phase change material after the completing of the fabricating including causing the second phase change material to heat to the curing temperature.
 3. The method of claim 2 wherein initiating curing of the second phase change material includes heating the second phase change material to an initiation temperature greater than or equal to the second phase change temperature.
 4. The method of claim 3 wherein the initiation temperature is less than the curing temperature.
 5. The method of claim 3 wherein the heating of the second phase change material causes a polymerization initiation catalyst suspended in the second phase change material to interact with a monomer suspended in the second phase change material.
 6. The method of claim 5 wherein the interaction of the polymerization initiation catalyst and the monomer is caused by the second phase change material flowing.
 7. The method of claim 3 wherein the initiation temperature is greater than or equal to the curing temperature.
 8. The method of claim 2 wherein causing the second phase change material to heat to the curing temperature includes exposing the second phase change material to ultraviolet (UV) radiation.
 9. The method of claim 1 wherein the curing temperature is less than the first phase change temperature.
 10. The method of claim 1 further comprising causing the second phase change material to cure, wherein the cured second phase change material is stable at the first phase change temperature.
 11. The method of claim 10 further comprising removing the first phase change material from the three-dimensional structure by heating the first phase change material to the first phase change temperature.
 12. The method of claim 1 wherein fabricating the three-dimensional structure includes forming a solidified three-dimensional support structure from the first phase change material where the solidified three-dimensional support structure defines cavity with a three-dimensional shape containing the second phase change material, the forming including: incrementally adding parts of the combination including depositing parts with both the first phase change material and the second phase change material, the depositing including, depositing the first phase change material in liquid form, causing solidification of the deposited first phase change material to form a part of the solidified support structure, and depositing the second phase change material contained by the support structure.
 13. The method of 1 wherein the first phase change material comprises a wax.
 14. The method of claim 12 wherein incrementally adding parts of the combination includes depositing a plurality of layers of material.
 15. The method of claim 14 wherein at least some layers of material of the plurality of layers of material are deposited using a jetting process. 